Method of and apparatus for heattreating granular materials in a gas current



. Nov. 9, 1965 H. DENNERT 3,216,125

METHOD OF AND APPARATUS FOR HEAT-TREATING GRANULAR MATERIALS IN A GAS CURRENT Filed March 9, 1962 United States Patent Claims. E01. 34-10 The present invention relates to a method of heat-treating granular materials in a gas current and more particularly to improvements in such a heat-treating method for the purpose of baking, calcining, or sintering the respective materials, in which the material is treated in a suspended state by means of a hot gas current in a reaction chamber which is provided with a draft which is directed opposite to the gas current, and in which the reaction chamber is charged and emptied intermittently. This known intermittent method of heating granular materials in a gas current has the important advantage over the numerous conventional continuous methods that the length of the period during which the material remains in the reaction chamber is independent of its granular size, which means that the finer as well as the coarser material remains for the same length of time in the reaction chamber. This is especially of importance in the treatment of expansible materials and especially expansible clay.

The present invention is based upon the following technical presumptions and conditions:

If a certain quantity of granular material is held in suspension in a reaction chamber by means of a gas current, a stratification occurs within the column which is formed by the granular material in accordance with the different granular sizes thereof and ranging from the coarsest size in the lowest layer to the smallest size in the highest layer. The fuel gas enters at its highest temperature into the lower end of the column and cools off progressively as it passes upwardly through the column so that the upper layers only come in contact with the gas when it has a considerably reduced temperature. This has the result that the coarsest :grain of an expansible material is expanded considerably more than the fine grain. The bulk weight of the individual fractions of the finally burned material therefore varies very strongly and it is impossible to attain a material with equal properties of all granular sizes.

While applying the previous manner of operation of maintaining the material in suspension in the gas current and charging and emptying the reaction chamber intermittently, it is an object of the invention to put the material by means of the ascending gas current into a vertical circulatory motion. The material is then taken along by the gas current in the ascending branch of the circulation and after reversing its direction, it rolls in the descending branch along the wall of the combustion chamber so that it can thereafter again be taken along upwardly by the gas current. According to the invention, the simple suspension of the material is therefore changed to a continuous circulating movement. This process may also be regarded as a suspension of the material with a circulating movement superimposed thereon. In the descending branch of the circulating movement, the material is subjected to gravity. Since the eddies of the gas current which are for-med in the reaction chamber because of the non-laminar flow of this current have likewise a downwardly directed component, they are assisting in returning the material along the wall of the combustion chamber to the starting point of its circulation.

In carrying out the process it is important to prevent the gas current from removing parts of the material from the apparatus. ing the reaction chamber of a suitable shape, namely, by making it in the form of a funnel with a relatively large generating angle of, for example, approximately 60. Since the velocity of flow of the gas entering at the neck of the funnel decreases rapidly because of the wide angle of the funnel, the buoyant force exerted upon the granular material also decreases accordingly.

It is, however, advisable to provide additional means for restraining the granular material, for example, a de flecting plate in front of the gas outlet port of the reaction chamber. It is also advisable to provide a trap, for example, in the form of a cyclone separator, at a point in the fiow of the gas subsequent to the combustion chamber so that the material which is separated in this trap will be returned therefrom into the reaction chamber.

The objects, features, and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying diagrammatic drawing of one preferred embodiment of the apparatus according to the invention.

In the drawing which illustrates the apparatus according to the invention while in operation during the treatment of the granular material, this apparatus comprises a reaction chamber 1, a burner 2 in a combustion chamber with a fuel supply line 3 connected thereto, and a control element 4 interposed in the fuel line. The combustion chamber and the reaction chamber 1 are connected by a channel 6 in which the flame of the burner can form which, however, cannot reach beyond the end of channel 6 so that only hot gas but no flame will enter into the reaction chamber 1. This chamber 1 is connected by a channel 7 with a container 8 into which new material may be supplied through a gate 9 and in which this material is preheated in a manner as subsequently described. The preheated material is passed from container 8 through the line 10 to the inlet port 11 of the reaction chamber in any suitable manner, as indicated diagrammatically by the dot-,

and-dash line 11. While the treatment is being carried out, the charging line 10 is closed by a flap 12 and then in the position as indicated in the drawing, which is done by means of a servo-drive 13, as indicated diagrammatically.

The air supply line 14 coming from the blower 5 branches olf into the two lines 15 and 16 which may be controlled by flaps 17 and 18 by means of a servo drive 19. In the operating condition of the apparatus as illustrated, flap 17 is open and flap 18 is closed.

Channel 6 is also connected to a flue 20 which is provided with a flap 21 which during the operation of the apparatus is held in the closed position, for example, by a spring 21'.

The lower end of the reaction chamber 1 is connected to a discharge pipe 22 which during the operation is held in the closed position by a suitable control member 23 which controls the connection between the reaction chamber 1 and a cooling chamber 24. This cooling chamber 24 is, in turn, connected to chambers 25 and 26 which may be shut off from each other by a further control member 27. Finally, the discharge port of chamber 26 which terminates into a discharge channel .29 for the treated material is closed during the operation of the apparatus by a control member 28. In order to simplify the illustration, control members 23, 27, and 28 are indicated in the form of valve cones, and likewise for the purpose of illustration it is assumed that they are jointly controlled by a servo drive 30.

Channel 15, which in the operating condition as illustrated is closed, terminates into channel 31 which leads to chamber 1.

Assuming that the process of treating the material in This may be attained primarily by design the reaction chamber is in progress, blower 5 then supplies air under pressure through line 14, channel 16, chamber 25, chamber 24, and channel 31 to the burner 2. The flame of the burner burns in channel 6, and the hot gas enters under pressure into the reaction chamber 1 which contains a certain quantity of the granular material which is to be expanded. Due to the constriction which is formed by the neck 32 of the reaction chamber 1, the velocity of flow of the gas is accordingly increased so that in the reaction chamber 1 a hot gas jet is formed which is closed to a certain extent and puts the granular material into a circulating motion, asindicated in the drawing, and thereby returns it to its starting point 32. In order to prevent the granular particles from being carried away by the gas, a conical deflecting plate 33 is provided near the upper end of reaction chamber 1 and additional deflecting plates 34 in front of the opening into gas channel 7. While the material carries out its circulating movement in chamber 1, the gas which is still very hot flows through channel 7 into the preheating chamber 8 in which it transmits its heat or a part thereof to the material in chamber 8 and then flows ofi either toward the outside or to a place where the residual heat is utilized.

Chamber 24 contains the material of the preceding charge which has already been treated. Since the cold air current which is supplied by the blower 5 through line 16 passes through this treated material in chamber 24, it is cooled, while at the same time the air in front of the burner 2 is preheated. The material in chamber 24 thus floats in a freely suspended condition in the air current.

After the material has remained in the reaction chamber 1 for a suflicient length of time to carry out the expanding process, it should be withdrawn from this chamber. For this purpose, flaps 17 and 18 are at first turned to their vertical position so that channel 16 is closed and channel is opened. The compressed air which is further supplied by the blower then passes through the channel section 36 directly to the burner 2 which is then shut oif or at least considerably throttled.

Since channel 16 is closed, the air current which previously held the granular material freely suspended in chamber 24 is shut oif so that, due to its gravity, the material drops through chamber 25 into chamber 26.

At this stage, the servo drive 30 is operated to open the valve members 23 and 28 and to close the valve member 27. The treated and cooled material in chamber 26 is then removed from the apparatus at 29. Simultaneously with the reversal of valve members 23, 27, and 28, flap 12 is also moved to its vertical position so that channel 7 is shut off and the flow of gas in chamber 1 is interrupted. The pressure which is then formed in channel 6 passes into the flue 20 and opens flaps 21 therein, so that the gas can then escape to the outside. Since valve member 23 is then in the open position, the hot material which has been expanded completely can leave the reaction chamber 1 through pipe 22 and drop into chambers 24 and 25, but no further since a screen 37 which has been moved together with valve members 23, 27, and 28 blocks the passage at 38.

When the next charge is to be treated, the position of flaps 12, 17, and 18 is reversed so that in chamber 24 behind screen 37 a pressure is produced of such a strength that the material will be held freely in suspension in chamber 24. Valve members 23, 27, and 28 may then also be reversed and chamber 1 may be newly charged since this new charge will be maintained in suspension by the compressed air from the blower.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood thatit is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. A method of treating a granular expansible mineral in a hot gas current to expand the granules thereof, comprising the steps of periodically charging an upwardly diverging reaction chamber with a batch of said granular mineral, injecting under pressure a current of hot gas of smaller cross-section than the cross-section of the reaction chamber into the lower end of said chamber, passing said current in the upward direction through said chamber and from said chamber through a charging and preheating chamber adapted to periodically receive new batches of the mineral to be treated in said reaction chamber for preheating at least the next new charge, said mineral in said reaction chamber being freely suspended in said current of hot gas in said chamber, and continuously subjected to a substantially vertical circulating movement of the granules in said reaction chamber in which, during the ascending part of said movement, said mineral granules are carried by said hot gas current to a point near the top of said chamber where said material is deflected downwardly whereupon, during the descending part of said movement, said mineral granules return outside the path of the hot gas current by gravity along the inclined wall of said chamber to the point of entry of said hot gas into said chamber, interrupting said gas current when said granules have been expanded, removing said expanded granules from said reaction chamber by gravity to a cooling chamber, then passing said next new batch of granules to be treated from said preheating chamber into said reaction chamber and passing said gas current therethrough and at substantially the same time passing a current of cold air under pressure in the upward direction through said cooling chamber so that said mineral therein is suspended in and cooled by said air current, interrupting said air current, opening said cooling chamber at its lower end to discharge said mineral granules therefrom by gravity, closing said lower end of said cooling chamber again and again removing the expanded granules of the last-treated mineral from said reaction chamber by gravity to said cooling chamber and cooling said last bath of expanded mineral granules in said cooling while a new preheated charge of said material is passed from said preheating chamber into and treated in said reaction chamber.

2. An apparatus for expanding mineral material in a hot gas comprising a source of hot gas, a discharge pipe through which hot gas from said source is directed vertically upward, said source of hot gas providing a high velocity flow of gas in said discharge pipe so that granular mineral material in said hot gas will be carried upwardly thereby, a reaction chamber having an annular wall diverging upwardly from said discharge pipe, flue means adjacent the top of said reaction chamber to lead the hot gas therefrom, baffle means in said reaction chamber to prevent the mineral material being treated from entering said flue means and to direct upwardly moving mineral particles outwardly and downwardly so that they will descend substantially to said discharge pipe to be again entrained and carried upwardly in said reaction chamber by said upward flow of hot gas, means to introduce a charge of granular mineral material into said reaction chamber, and means to interrupt the flow of hot gas from said source through said discharge pipe whereby a charge of material that has been treated and expanded will be discharged by gravity from said reaction chamber through said discharge pipe.

3. The device of claim 2, in which said flue means is connected to a preheat chamber in which material to be later treated in said reaction chamber may be preheated by the hot gas from said reaction chamber.

4. The device of claim 2, in which a cooling chamber is provided below said reaction chamber to receive said treated mineral by gravity upon interruption of said flow of gas.

5. The device of claim 4, in which the source of said flow of hot gas is a burner and in which branched duct means are provided to lead air to said burner selectively through said cooling chamber to cool treated mineral therein, or directly to said burner.

6. The device of claim 5, in which said cooling chamber is in the form of a cone with its apex connected to one branch of said duct so that air entering said cooling chamher from said duct will pass upwardly through said treated material, said duct means being arranged to operate as a discharge passage through which cooled treated material is discharged.

7. A device for treating expandable material with hot gas comprising burner means to provide hot gas at a high velocity, a reaction chamber provided with upwardly divergent walls at its lower portion and deflector means adjacent its upper portion to deflect upwardly moving particles radially outwardly of said reaction chamber, first flue means leading the high velocity hot gas to discharge vertically into the bottom of said reaction chamber, second flue means connected to the upper portion of said reaction chamber above said deflector means to carry exhaust gases from said reaction chamber, a material supply chamber, said second flue means being connected to said material supply chamber to pass the gases from said reaction chamber through material in said material supply chamber, valved duct means connecting the lower extremity of said material supply chamber to said reaction chamber whereby a charge of material may be moved by gravity from said material supply chamber to said reaction chamber, a downwardly extending discharge passage connected to said first flue means axially below said reaction chamber, a cooling chamber connected to said discharge passage and positioned to receive material discharged by gravity from said reaction chamber, means to interrupt the flow of hot gas at high velocity whereby a charge of material in said treating chamber will be transferred by gravity into said cooling chamber, and means to selectivity direct air to said cooling chamber or directly to said burner means to provide hot gas.

8. A method of treating a granular mineral material in a reaction chamber of a downwardly tapered conical shape having a single aperture at its lower extremity, the steps of providing a relatively small diameter upwardly directed jet of hot combustion gas axially upwardly through said aperture at the apex of said conical reaction chamber,

introducing a batch of granular mineral to be treated into said reaction chamber so that said granular mineral material will fall by gravity downwardly and inwardly into said upwardly directed jet of hot gas at said apex to be entrained and carried upwardly by said gas, deflecting said granular material radially outwardly of said jet of hot gas so that it again falls by gravity downwardly to said upwardly directed jet of hot gas, continuing to treat said batch of granular material in said reaction chamber until said material is completely treated, interrupting said jet of hot gas to permit said treated granular material to flow downwardly from said reaction chamber through said aperture, re-establishing said jet of hot gas, and introducing a second batch of granular material.

9. The method of claim 8, in which said batch of granular material, prior to introduction into said reaction chamber, is subjected to a heating step, the medium for said heating step being the hot gas from said reaction chamber passing through said batch of granular material.

10. The method of claim 8, including the steps of cooling treated material that has flowed downwardly from said reaction chamber by passing air therethrough and using the air from the cooling step to provide combustion air to produce said hot combustion gas.

References Cited by the Examiner UNITED STATES PATENTS 2,105,778 1/38 Behr 3457 2,435,927 2/48 Manning et a1. 3457 X 2,538,833 1/51 Rycke 3457 2,561,394 7/51 Marshall 1594 X 2,602,498 7/52 Overton 3492 X 2,621,034 12/52 Stecker 263-21 2,853,241 9/58 Gindofl et a1 252378 X 3,020,646 2/ 62 Joseph et a1. 3457 X 3,028,681 4/62 Jorman 3457 3,078,588 2/63 Mark 3457 3,118,658 1/64- Dennert 252378 X FOREIGN PATENTS 1,170,454 1/59 France.

516,163 12/39 Great Britain.

WILLIAM F. ODEA, Acting Primary Examiner.

NORMAN YUDKOFF, Examiner. 

2. AN APPARATUS FOR EXPANDING MINERAL MATERIAL IN A HOT GAS COMPRISING A SOURCE OF HOT GAS, A DISCHARGE PIPE THROUGH WHICH HOT GAS FROM SAID SOURCE IS DIRECTED VERTICALLY UPWARD, SAID SOURCE OF HOT GAS PROVIDING A HIGH VELOCITY FLOW OF GAS IN SAID DISCHARGE PIPE SO THAT GRANULAR MINERAL MATERIAL IN SAID HOT GAS WILL BE CARRIED UPWARDLY THEREBY, A REACTION CHAMBER HAVING AN ANNULAR WALL DIVERGING UPWARDLY FROM SAID DISCHARGE PIPE, FLUE MEANS ADJACENT THE TOP OF SAID REACTION CHAMBER TO LEAD THE HOT GAS THEREFROM, BAFFLE MEANS IN SAID REACTION CHAMBER TO PREVENT THE MINERAL MATERIAL BEING TREATED FROM ENTERING SAID FLUE MEANS AND TO DIRECT UPWARDLY MOVING MINERAL PARTICLES OUTWARDLY AND DOWNWARDLY SO THAT THEY WILL DESCEND SUBSTANTIALLY TO SAID DISCHARGE PIPE TO BE AGAIN ENTRAINED AND CARRIED UPWARDLY IN SAID REACTION CHAMBER BY SAID UPWARD FLOW OF HOT GAS, MEANS TO INTRODUCE A CHARGE OF GRANULAR MINERAL MATERIAL INTO SAID REACTION CHAMBER, AND MEANS TO INTERRUPT THE FLOW OF HOT GAS FROM SAID SOURCE THROUGH SAID DISCHARGE PIPE WHEREBY A CHARGE OF MATERIAL THAT HAS BEEN TREATED AND EXPANDED WILL BE DISCHARGED BY GRAVITY FROM SAID REACTION CHAMBER THROUGH SAID DISCHARGE PIPE. 